The invention discloses a passivation technology of an aluminum alloy cylinder cover. A passivation liquid used by the passivation technology comprises 4-6g/L of sodium silicate, 13-15g/L of titanium dioxide, 20-23g/L of nitric acid having a concentration of 68%, 15-17g/L of potassium permanganate, 3-5g/L of sodium peroxide, 6-8g/L of ammonium bifluoride, 22-24g/L of ferrous chloride, 5-9g/L of chromium nitrate, 3-5g/L of zirconium nitrate, 14-16g/L of sodium dodecylsulfate and the balance water. The passivation technology comprises the following steps of 1, carrying out alkali washing and carrying out cleaning by clear water, 2, carrying out pickling and carrying out cleaning by clear water, 3, preparing the passivation liquid from the above components, putting the passivation liquid into a passivation tank, diluting the passivation liquid by 4-6 times, controlling a temperature of the passivation liquid in a range of 35-45 DEG C and a pH value in a range of 3-5, putting a supersonic generator at the bottom of the passivation tank, carrying out passivation for 13-17min, then carrying out cleaning by water and carrying out natural drying.